Ion mobility spectrometry, heretofore referred to as plasma chromatography in the technical and patent literature, has evolved into a tool having important application in the field of vapor detection and analysis. The applicants' early work in this field is disclosed, inter alia, in U.S. Pat. Nos. 3,699,333; 3,526,137; 3,593,018; 3,596,088; 3,621,239; 3,621,240; 3,624,389; 3,626,178; 3,626,179; 3,262,180; 3,262,181; 3,262,182; 3,629,574; 3,639,757; 3,668,381; 3,668,383; 3,668,385; 3,697,748; 3,697,749; 3,742,213; 3,812,355; 3,845,301; and, 4,195,513.
The extraction of vapor samples from luggage to detect explosives has been the subject of research and development in the U.S. Department of Transportation and others.
The subject matter of the present invention encompasses several improvements in Ion Mobility Spectrometer (hereinafter sometimes abbreviated as IMS) instrumentation for special applications in detecting high molecular weight explosive vapors, illegal drug vapors, or contaminants such as carcinogens and dioxins by sophisticated "sniffing" and analyzing apparatus. Condensible vapors, aerosols, chlorinated fluorocarbons, and fine particulates also may be collected and analyzed for the presence of illegal or dangerous substances.
The Model LRV-1 IMS instrument of PCP, Inc., West Palm Beach, Florida, is the basis for a new and improved large reaction volume IMS system (LRVIMS) of superior response and air flow characteristics, which will, in conjunction with other features, be described in the following detailed description of the invention.
The "new detection concepts" and both new instrument system features using the Ion Mobility Spectrometer will be described hereinafter especially with reference to detection of explosive vapors, such as TNT and RDX, in airport screening applications seeking to detect explosives hidden in baggage or on passengers.